We analyzed the relationship between incidence rates of chronic respiratory symptoms over 13 years and occupational exposure during the first five years of follow-up. The study group contained 1132 males and 1598 females, 19 to 60 years of age, randomly selected from residents of Cracow, Poland. The data was collected in three surveys conducted in 1968, five and 13 years later. Prolonged occupational exposure (i.e. reported in the initial survey and 5 years later) to dusts doubled the odds for the appearance of chronic phlegm and attacks of breathlessness in all men, and of chronic bronchitis in men aged 41 to 50, initially free of the symptom. In women, this exposure doubled the odds for new chronic cough and for chronic bronchitis. Prolonged exposure to chemicals doubled the incidence rates of attacks of breathlessness and dyspnea in all women and of chronic bronchitis in women with the lowest level of education. Prolonged work in variable temperatures doubled the risk of wheeze in women. The effects of discontinuation or start of exposure during the initial 5 years of the study were also seen on the incidence rates of the symptoms but were less pronounced. The detected effects of occupational exposure were not modified by cigarette smoking or living in areas of the city with various levels of air pollution. This longitudinal analysis confirms the results of cross-sectional studies which have indicated deleterious effects of even moderate occupational exposures on respiratory symptoms.